Catheter with improved loop contraction and greater contraction displacement

ABSTRACT

A catheter with a variable circular loop is responsive to a contraction wire for increasing the coiling of the circular loop. The shape of the loop is supported by an elongated member, wherein a radially constrictive sleeve confines the contraction wire to extends immediately alongside the length of elongated member so as to improve uniformity and minimize misshaping of the loop during contraction.

FIELD OF INVENTION

This invention relates generally to methods and devices for invasivemedical treatment, and specifically to catheters, in particular,catheters having distal sections adapted for mapping and ablatingselected anatomy.

BACKGROUND

Ablation of myocardial tissue is well known as a treatment for cardiacarrhythmias. In radio-frequency (RF) ablation, for example, a catheteris inserted into the heart and brought into contact with tissue at atarget location. RF energy is then applied through an electrode on thecatheter in order to create a lesion for the purpose of breakingarrhythmogenic current paths in the tissue.

Circumferential ablation of the ostia of the pulmonary vein is nowaccepted as a treatment for atrial arrhythmias, and particularly foratrial fibrillation. For example, U.S. Pat. No. 6,064,902, whosedisclosure is incorporated herein by reference, describes a catheter forablating tissue on the inner wall of a blood vessel, such as a pulmonaryvein. The tip portion of the catheter is deflectable from a first,generally straight, configuration, in which the proximal and distalsections are substantially co-linear, to a second, J-shaped,configuration in which the proximal and distal sections are generallyparallel with a separation therebetween substantially corresponding tothe inside diameter of the blood vessel. The distal end portion of thecatheter is rotated about the longitudinal axis of the catheter to causea circumferential displacement of proximal and distal ablationelectrodes on the catheter along the inner wall of the pulmonary vein.In this way, the electrode catheter may be used to ablate a number ofcircumferentially-spaced sites on the inner wall of the pulmonary veinby ablating one or two sites at each circumferential position.

U.S. Pat. No. 6,973,339, whose disclosure is incorporated herein byreference, describes a lasso for pulmonary vein mapping and ablation. Acatheter for circumferentially mapping a pulmonary vein (PV) includes acurved section shaped to generally conform to the shape of the interiorsurface of the PV. The curved section is connected to catheter by agenerally straight axial base section that is in an “on edge”configuration where the base axial section connects to the curvedsection on the circumference of the curved section. The curved sectioncomprises one or more sensing electrodes, and its proximal end is joinedat a fixed or generally known angle to a base section of the catheter.Position sensors are fixed to the curved section of the catheter and tothe distal end of the base section. The catheter is inserted into theheart, and the curved section is positioned in contact with the wall ofthe PV, while the base section remains within the left atrium, typicallypositioned such that the joint with the curved section is at the ostiumof the vein. The information generated by the three position sensors isused to calculate the locations and orientations of the sensingelectrodes, which enables mapping of the surface of the PV. The sensingelectrodes may additionally perform ablation of selected sites, or thecatheter may further comprise ablation elements.

U.S. Pat. No. 7,008,401, whose disclosure is incorporated herein byreference, describes compound steering assemblies, usable in bothdiagnostic and therapeutic applications, for steering the distal sectionof a catheter in multiple planes or complex curves. These assemblies aresaid to enable a physician to swiftly and accurately position andmaintain ablation and/or mapping electrodes in intimate contact with aninterior body surface. U.S. Pat. No. 5,820,591, whose disclosure isincorporated herein by reference, similarly describes compound steeringassemblies of this sort.

U.S. Pat. No. 8,608,735 whose disclosure is incorporated herein byreference, describes a medical device, including an insertion shaft,having a longitudinal axis and having a distal end adapted for insertioninto a body of a patient. A resilient end section is fixed to the distalend of the insertion shaft and is formed so as to define, whenunconstrained, an arc oriented obliquely relative to the axis and havinga center of curvature on the axis. One or more electrodes are disposedat respective locations along the end section.

However, because human anatomy varies between individuals, the shape andsize of an ostium vary, and the arcuate distal section may not alwaysfit the particular target ostium. Moreover, it may be desirable to usethe same catheter for a target ostium of a certain diameter and also thePV of that ostium which may have a significantly lesser diameter.Additionally, where a lasso catheter may have a variable arcuate distalassembly, contraction of the arcuate distal assembly may misshapen thegenerally circular form of the arcuate distal assembly because one ormore of the components thereof are too stiff for tighter coiling in adesirable manner.

Current circular loop catheters are constructed utilizing a supportmember, e.g., a nitinol spine, with a constant uniform cross-sectionthat fails to consistently maintain a circular configuration during loopcontraction. Such current circular loop catheters also are limited inits contraction and deflection characteristics in requiring more poundcontraction wire tensile force for less loop contraction. Moreover,current circular loop catheters may lack reliable attachment between thecontraction wire and the support member that would eliminate possiblebreakage or release of the contraction wire from the support member.Current circular loop catheters have nitinol spines with the sameuniform area moments of inertia along their entire length and thenitinol spines have the same cross-sectional area.

SUMMARY OF THE INVENTION

The present invention is directed to a catheter having a variablearcuate distal with improved contraction and bending radiuscharacteristics, along with greater durability.

The variable arcuate distal section includes a shape-memory supportmember, a contraction wire, and a radially-constrictive tubing or sleeveto greatly increase the degree of contraction of a generally circularcatheter loop while decreasing the forces on the contraction wire andall other structural support portions of the loop and providingoperators of the catheter with a repeatable and more truthful roundcontraction for circular diagnostic and therapeutic catheters.

In some embodiments, the radially-constrictive tubing is transparent orat least translucent so that the contraction wire under the tubing isvisible, especially during assembly of the variable arcuate distalsection.

In some embodiments, the radially-constrictive tubing has a braidedconstruction so that its radial constriction is increased when tensionis applied to the tubing in a longitudinal direction.

In some embodiments, the radially-constrictive tubing is constructed ofa manufactured fiber, spun from a liquid crystal polymer (LCP), forexample, manufactured fiber sold under the trademark VECTRAN®, createdby Celanese Acetate LLC and now manufactured by Kuraray Co., Ltd.

In some embodiments, an electrophysiology catheter includes an elongatedcatheter body, a contraction wire, and a distal assembly configured forcontraction by actuation of the contraction wire. The distal assemblyhas a shape-memory support member having a 3-D configuration with adistal portion defined by a distal radius.

In more detailed embodiments, the support member has an inner sidefacing an inner circumference of the 3-D configuration, wherein acoextensive portion of the contraction wire extending through the distalassembly is aligned with the inner side.

In some detailed embodiments, the distal assembly includes a radiallyconstrictive tubing surrounding the support member and a coextensiveportion of the contraction wire with the support member.

In some detailed embodiments, the support member and the coextensivesegment of the contraction wire jointly define a cross-sectionalprofile, and the radially constrictive tubing surrounds the supportmember and the coextensive segment generally in conformity to thecross-sectional profile.

In some detailed embodiments, the coextensive portion of the contractionwire is aligned with a flat side of the support member and configured tomaintain the coextensive segment of the contraction wire generally inalign the flat side during contraction of the distal assembly.

In some embodiments, an electrophysiology catheter has an elongatedcatheter body defining a longitudinal axis, a contraction wire, and a3-D distal assembly movable between a neutral configuration and acontracted configuration in response to longitudinal movement of thecontraction wire. The 3-D distal assembly has at least an elbow definedby a proximal diameter and a distal portion defined by a distaldiameter, and a radially constrictive tubing that extends generallybetween the elbow junction and the distal portion. For the neutralconfiguration, the proximal diameter is less than the distal diameter.For the contracted configuration, the distal diameter is about equal toor less than the proximal diameter.

In some detailed embodiments, the elbow junction has a twist configuredto support the distal portion generally transversal to the longitudinalaxis such that the longitudinal axis extends through a center of thedistal portion.

In some detailed embodiments, the distal assembly has an elongatedsupport member having an inner flat side and an opposing flat side, andwherein the contraction wire has a distal segment coextensive with theinner flat side along its entire length.

In some detailed embodiments, the inner side of the support member is onor near an inner circumference of the distal portion of the 3-D distalassembly.

In some embodiments, the distal assembly further includes aradially-constrictive tubing circumferentially surrounding at least aportion of the elongated support member and a friction-reducing tubingsurrounding a portion of the contraction wire.

In some embodiments, the radially-constrictive tubing iscircumferentially constrictive around the support member and thefriction-reducing tubing in minimizing lateral movement of thecontraction wire relative to the support member.

In other embodiments, an electrophysiology catheter has an elongatedcatheter body defining a longitudinal axis, a contraction wire, and adistal assembly with a 3-D arcuate form, the distal assembly movablebetween a neutral configuration and a contracted configuration inresponse to longitudinal movement of the contraction wire. The distalassembly has a support member providing the 3-D arcuate form, the 3-Darcuate form having an elbow junction and a distal portion, the elbowjunction defined by at least a proximal diameter and the distal portiondefined by a distal diameter, and a radially constrictive tubingsurrounding the support member and a coextensive portion of thecontraction wire. For the neutral configuration, the proximal diameteris less than the distal diameter. For the contracted configuration, thedistal diameter is decreased to a diameter about less than the distaldiameter.

In some detailed embodiments, the 3-D arcuate form defines an innercircumference, the distal assembly includes a tubing with multiplelumens including a lumen closest to the inner circumference, and thesupport member and the coextensive portion of contraction wire are inthe lumen closest to the inner circumference.

In some detailed embodiments, the support member has agenerally-rectangular cross-section, the support member having a distalportion wherein a width dimension and a height dimension of thegenerally rectangular cross-section varies along the length of thedistal portion.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the present invention will bebetter understood by reference to the following detailed descriptionwhen considered in conjunction with the accompanying drawings. It isunderstood that selected structures and features have not been shown incertain drawings so as to provide better viewing of the remainingstructures and features.

FIG. 1 is a top plan view of a catheter of the present invention,according to one embodiment.

FIG. 2A is a detailed view of a 3-D arcuate distal assembly of thecatheter of FIG. 1, in a neutral, unconstrained configuration.

FIG. 2B is the detailed view of the 3-D arcuate distal assembly of FIG.2, in a contracted configuration.

FIG. 3 is an end cross-sectional view of a catheter body of the catheterof FIG. 1, taken along line A-A.

FIG. 4 is an end cross-sectional view of a deflectable intermediatesection of the catheter of FIG. 1, taken along line B-B.

FIG. 5A is an end cross-sectional view of a connector section of thecatheter of

FIG. 1, taken along line C-C.

FIG. 5B is a side cross-sectional view of the connector section of FIG.1, taken along area D-D.

FIG. 6A is a perspective view of a support member and a coextensivecontraction wire, along with a radially-constrictive tubing.

FIG. 6B is a detailed top view of an assembled structure of distal endsof the support member and the contraction wire of FIG. 6A.

FIG. 6C is a perspective view of a radially-constrictive tubing, inaccordance with an embodiment of the present invention.

FIG. 6D is a perspective view of a radially-constrictive tubing, inaccordance with another embodiment of the present invention.

FIG. 7 is an end view of the distal assembly of FIG. 1.

FIG. 8 is an end cross-sectional view of the distal assembly of FIG. 2A,taken along line E-E.

FIG. 9 is a side cross-sectional view of the distal assembly of FIG. 2A,taken along line F-F.

FIG. 10 is a perspective view of an irrigated ablation electrode withlead wire attachments, according to one embodiment.

FIG. 11 is a side cross-sectional view of a control handle, inaccordance with one embodiment.

FIG. 12 is a partial top cross-sectional view of the control handle ofFIG. 11.

FIG. 13A is an end cross-sectional view of the support member of FIG.6A, before reshaping.

FIG. 13B is an end cross-sectional view of the support member of FIG.6A, taken along line G-G.

FIG. 13C is an end cross-sectional view of the support member of FIG.6A, taken along line J-J.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention that are described hereinbelowprovide probes, such as catheters, with improved arcuate distalelectrode-carrying structures, to facilitate maneuvering and positioningin the heart and especially tubular regions of different sizes in apatient's body and different circumferential locations within thetubular regions. Such catheters can be used to produce generallycircular or helical ablation paths, as well as sensing electricalactivity along a generally curve or helical pattern for electricalpotential and anatomical mapping.

Referring to FIG. 1, a catheter 10 according to the disclosedembodiments comprises an elongated body that may include a flexibleinsertion shaft or catheter body 12 having a longitudinal axis 13, andan intermediate section 14 distal of the catheter body that can be uni-or bi-directionally deflected off-axis from the longitudinal axis 13. Asshown in FIG. 2A, extending from the intermediate section 14 is aresilient three-dimensional (3-D) arcuate distal assembly 17 which isadvantageously constructed for significantly greater and more uniformloop contraction. As explained below in further detail, the distalassembly 17 is responsive to operator manipulation of a control handle16 in decreasing its radius and increasing its coiling, as shown in FIG.2B.

In the depicted embodiment of FIG. 1 and FIG. 3, the catheter body 12comprises an elongated tubular construction having a single, axial orcentral lumen 18. The catheter body 12 is flexible, i.e., bendable, butsubstantially non-compressible along its length. The catheter body 12can be of any suitable construction and made of any suitable material.In some embodiments, the construction comprises an outer wall 20 made ofpolyurethane or PEBAX. The outer wall 20 comprises an imbedded braidedmesh of stainless steel or the like, as is generally known in the art,to increase torsional stiffness of the catheter body 12 so that, whenthe control handle 16 is rotated, the intermediate section 14 willrotate in a corresponding manner.

The outer diameter of the catheter body 12 is not critical, but in someembodiments is no more than about 8 french, more preferably 7 french.Likewise the thickness of the outer wall 20 is not critical, but is thinenough so that the central lumen 18 can accommodate any desired wires,cables and/or tubes. The inner surface of the outer wall 20 is linedwith a stiffening tube 22 to provide improved torsional stability. Theouter diameter of the stiffening tube 22 is about the same as orslightly smaller than the inner diameter of the outer wall 20. Thestiffening tube 22 can be made of any suitable material, such aspolyimide, which provides very good stiffness and does not soften atbody temperature.

The deflectable intermediate section 14 comprises a shorter section oftubing 23 having multiple lumens, most of which are occupied by thevarious components passing from the catheter 12 and into theintermediate section 14. In the illustrated embodiment of FIG. 4, thereare six lumens. Coupled to the ring electrodes 19, respective leadwire/thermocouple pairs 40, 41 pass through a first lumen 31. Anonconductive protective sheath 39 may be provided to surround the wirepairs 40/41. An irrigation tubing 43 for delivering irrigation fluid tothe distal assembly 17 passes through a second lumen 32. For enablingdeflection of the intermediate section 14, a deflection puller wire 44passes through a third lumen 33. A position sensor cable assembly 48,including one or more single axis sensors (SAS) carried in the distalassembly 17, passes through a fourth lumen 34. To render an arcuatedistal portion 15 of the distal assembly 17 variable in shape and size,e.g., curvature radii, in response to manipulation of the control handleby a user, a contraction wire 24 passes through a sixth lumen 36. Asdescribed below, the contraction wire 24 acts on an elongatedshape-memory support member 50 that provides the 3-D shape of the distalassembly 17.

The multi-lumened tubing 23 of the intermediate section 14 is made of asuitable non-toxic material that is preferably more flexible than thecatheter body 12. A suitable material is braided polyurethane or PEBAX,i.e., polyurethane or PEBAX with an embedded mesh of braided stainlesssteel or the like. The plurality and size of the lumens are notcritical, provided there is sufficient room to house the relevantcomponents. In the illustrated embodiment, the third and sixth lumens 33and 36 for the deflection puller wire 44 and contraction wire 24 areoff-axis and diametrically opposed to each other, and the fifth lumen 35for the support member 50 is on-axis.

The useful length of the catheter, i.e., that portion that can beinserted into the body excluding the distal assembly 17, can vary asdesired. Preferably the useful length ranges from about 110 cm to about120 cm. The length of the intermediate section 14 is a relatively smallportion of the useful length, and preferably ranges from about 3.5 cm toabout 10 cm, more preferably from about 5 cm to about 6.5 cm.

Distal the intermediate section 14 is the distal assembly 17. Extendingbetween the intermediate section 14 and the distal assembly 17 is agenerally straight connector section 30, as shown in FIG. 2A and FIG.5A, having a tubing of suitable material, e.g., PEEK, with a centrallumen 37 that allows the various components extending between theintermediate section 14 and the distal assembly 17 to reorient andreposition as needed for transitioning therebetween, as shown in FIG.5B. The components are potted in the lumen 37 of the connector section30 by a suitable materials, for example, adhesive 112. Supporting thedistal assembly 17 and providing its 3-D shape, the shape-memory supportmember 50 extends proximally from the distal assembly 17 for arelatively short distance into a distal portion of the connector section30.

As shown in FIG. 2A and FIG. 6, the 3-D distal assembly 17 includes apreformed, arcuate distal portion 15, an elbow portion 21, and aproximal linear stem 26. The arcuate distal portion 15 carries aplurality of irrigated ring electrodes 19. The elbow portion 21 isconfigured to orient the distal portion 15 obliquely to the longitudinalaxis 13 such that the longitudinal axis extends generally through acenter of the distal portion 15, as shown in FIG. 7. As such, an obliqueangle e (FIG. 2A) is defined between the longitudinal axis 13 and aplane P generally defined by the distal assembly 17, wherein the obliqueangle ⊖ ranges between about 45 degrees and 135, preferably about 75 and100 degrees, and preferably about 90 degrees.

With reference to FIG. 2A, FIG. 6 and FIG. 7, the elbow portion 21 has aproximal curved section 21P, an elbow junction or “twist” 42, and adistal curved section 21D. The proximal curved section 21P traces afirst arc defined by a first (or proximal) radius R1 relative to thelongitudinal axis 13. The distal curved section 21D traces a second arcdefined by a second (or mid) radius R2 relative to an axis 27 oblique tothe longitudinal axis 13. The first radius R1 is lesser than the secondradius R2. However, both radii R1 and R2 are lesser than a third (ordistal) radius R3 defining a third arc traced by the distal portion 15.In some embodiments, the radius R1 ranges between about 0.1″ and 0.25″,the radius R2 ranges between about 0.15″ and 0.38″, and the radius R3ranges between about 0.4″ and 0.6″. As such, the 3-D configuration ofthe distal assembly 17, when unconstrained, has a spiral characteristic,with radius R3 being greater than the radius R2. For example, where theoblique angle ⊖ is about 90 degrees and the longitudinal axis 13 definesa Z axis, the first arc defined by radius R1 may lie in the Y/Z plane,and the second and third arcs defined respectively by radii R2 and R3may both lie in the X/Y plane, as shown in FIG. 6. It is understood thatthe distal assembly 17 is not limited to the radii R1, R2 and R3described above, and may contain more or less radii, as needed ordesired.

The 3-D configuration of the distal assembly 17, when unconstrained,also has a helical characteristic in that the distal assembly 17 extendsdistally as it spirals such that the distal end 25 of the distalassembly 17 is the distal-most portion of the distal assembly 17, asbest shown in FIG. 2A.

Accordingly, the distal assembly 17 has a spiral-helical configuration(or helical-spiral configuration) such that there are a first separationgap between the distal end 25 and the distal curved section 21D alongthe longitudinal axis 13, and a second separation gap between the distalend 25 and the distal curved section 21D along the oblique axis 27. Thespiral-helical configuration of the distal assembly 17 can be describedas tracing from its proximal end to its distal end an enlarging helixthat is on-axis with the longitudinal axis, as shown in FIG. 2A.

Depending on the length of the distal portion 15, the distal assembly17, in its neutral, unconstrained 3-D configuration, may subtend aradial angle a of about 360 degrees between the twist 42 and the distalend 25. In another embodiment, the distal assembly 17 subtends a radialangle α (FIG. 6) greater than 360 degrees, e.g., about 380 degrees. Whenthe distal assembly 17 is contracted, as shown in FIG. 2B, thespiral-helical form “coils up” and tightens, with the one or more ofradii R1, R2, R3 traced by the distal assembly 17 decreasing, and theradial angle α subtended by the distal assembly 17 increasing, forexample, from about 360 or 380 degrees to about 540 degrees or morebetween the twist 42 and the distal end 25. Accordingly, the distalassembly 17 in its neutral, unconstrained configuration may be used forcircumferential contact with an ostium having a larger radius, and thenbe adjusted into its contracted configuration for circumferentialcontact within the PV of the ostium with a significantly smaller radius.

As shown in FIG. 8, the distal assembly 17 includes a multi-lumenedtubing 56. In the disclosed embodiment, the tubing 56 has four off-axislumens, namely, a first lumen 51 for the SAS cable assembly 48(circumferentially surrounded by a friction-reducing coating 38, e.g.,of TEFLON®), a second lumen 52 for the ring electrode wire pairs 40, 41,a third lumen 53 for irrigation fluid delivered through the irrigationtubing 43, and a fourth lumen 54 for the support member 50 and thecontraction wire 24, a segment of which is coextensive with the supportmember 50 in the lumen 54. Again, position and sizing of the lumens arenot critical, except the position of the fourth lumen 54 for thecontraction wire 24 is preferably on or near an inner circumference ofthe spiral-helical form of the distal assembly 17 so that proximalmovement of the wire 24 can act more effectively in tightening thespiral-helical form and increasing its coiling. The multi-lumened tubing56 can be made of any suitable material, and is preferably made of abiocompatible plastic such as polyurethane or PEBAX.

In the depicted embodiment, the pre-formed support member 50 of thedistal assembly 17 extends through the fourth lumen 54 of the tubing 56to provide and define the 3-D spiral-helical shape of the distalassembly 17, which includes the twist 42 and arcs of the proximalsection 21P and the distal section 21D, and the distal portion 15defined by radii R1, R2 and R3. The support member 50 is made of amaterial having shape-memory, i.e., that can be straightened or bent outof its original shape upon exertion of a force and is capable ofsubstantially returning to its original shape upon removal of the force.In some embodiments, a suitable material for the support member 50 is anickel/titanium alloy. Such alloys typically comprise about 55% nickeland 45% titanium, but may comprise from about 54% to about 57% nickelwith the balance being titanium. One nickel/titanium alloy is Nitinol,which has excellent shape memory, together with ductility, strength,corrosion resistance, electrical resistivity and temperature stability.

In some embodiments, as shown in FIG. 5A, the support member 50 has aproximal end received and affixed in the connector section 30 In someembodiments, the proximal end of the support member 50 extends at adepth of about 2-3 mm proximal of the distal end of the connectorsection 30. Alternatively, the support member 50 can extend furtherproximally into the lumen 35 of the intermediate section 14, through theentire length of the intermediate section 14, and even into the catheterbody 12 via the central lumen 18, as desired or appropriate.

Advantageously, the support member 50 has a generally rectangularcross-sectional shape whose height and width dimensions vary in apredetermined manner along the length of the member 50. As shown in FIG.13B and FIG. 13C, the generally rectangular cross-sectional area at anylocation along the length remains constant although its width dimensionW and height dimension vary at different locations. There is noreduction or increase in the cross-sectional area at any location alongthe length in that any loss or gain in one dimension is proportionallygained or lost by the other dimension between a more proximal locationand a more distal location along the length of the support member 50. Asa tapered portion or “tail” of the support member 50 narrows in onedimension of the cross-sectional area from the proximal end to thedistal end of the member, the other dimension of the cross-sectionalarea widens from the proximal end to the distal end. The dimension thatdecreases (for example, the width dimension W along the X axis in FIG.13B and FIG. 13C) decreases its resistance to bending in that dimensionfrom the proximal end to the distal end, while the dimension thatincreases (for example, the height dimension H along the Y axis in FIG.13B and FIG. 13C) increases its resistance to bending in that dimensionfrom a proximal end to a distal end of the tapered portion.

As shown in FIG. 6, the generally rectangular cross-section of thesupport member 50 at its proximal end has a maximum width W1 and aminimum height H1. For minimizing change or deformation in radii R1 andR2 during contraction of the distal assembly 17, the width and heightdimensions of the cross-sectional area of the support member 50 begin tochange (or taper) starting at a predetermined location distal of radiusR2 (e.g., at or around location L2) Distal of the predeterminedlocation, in the tapered tail of distal assembly 17, the width begins todecrease to W2 (<W1) while the height begins to increase to H2 (>H1).The width further decreases to W3 (<W2<W1) while the height furtherincreases to H3 (>H2 >H1) at distal location L3. These decreases andincreases are smooth and continuous. This tapered configuration biasesthe support member 50 to have increasing less resistance to coilingtoward the distal end 25 such as when contracted by the contraction wire24, while providing increasingly more resistance to oblique forcestoward the distal end 25 such as when the distal assembly 17 contactstissue surface head on. Thus, this varied cross-sectional shape allowsthe distal assembly 17 to exhibit improved contraction characteristics,including the distal portion 15 being able to contract and coil readilywith minimal deformation of the elbow junction 21 and the elbow junction21 being better able to withstand the load from an axial force that isapplied when the distal assembly 17 comes into contact with targettissue. With this varied cross-sectional shape applied to the supportmember 50, the distal assembly 17 can be adjusted, upon actuation of thecontraction wire 24, to assume a smaller loop size (see FIG. 2B), forexample, where the distal portion 15 assumes a curvature that isgenerally equal to or even be lesser than the curvature of the distalsection 21D.

As shown in FIG. 6, with a generally rectangular cross-section, thesupport member 50 resembles a “coiled ribbon” having sides/surfaces 62and 63 defining a height dimension of the generally rectangularcross-section, and edges 75 defining a width dimension of the generallyrectangular cross-section. Advantageously, the inner flat side/surface62, along its length, continually faces the inner circumference of thespiral-helical configuration of the distal assembly, and an outer flatside/surface 63 that is opposite of the inner flat surface 62continually faces outwardly, away from the inner circumference of thespiral-helical configuration. The tapering of the support member 50results in the “tapered tail” of the distal assembly 17 resembling anincreasing wider and thinner ribbon.

Moreover, the generally rectangular cross-section at the proximal end ofthe support member 50 helps anchor the proximal end in the lumen 35 ofthe tubing 23 of the deflectable section 14 and reduces the risk of thesupport member rotating about its axis where the proximal end is pottedby an adhesive, e.g., epoxy (see FIG. 4).

In some embodiments, the support member 50 begins with a roundcross-sectional shape, as shown in FIG. 13A. The support member 50, forexample, a round wire, is progressively flattened to produce thegenerally rectangular cross-section and tapered tail. Thus, the twoopposed ends of the width dimension between the parallel fattenedsurfaces of the height dimension carry the residual round shape of theoriginal round cross-sectional shape. It is understood that the supportmember may begin with a square/rectangular cross-sectional shape whichwould then result in flat opposed ends instead of round opposed ends. Insome embodiments, using a round wire may be more economical tomanufacture, and rounded opposed ends may ease the assembly of thedistal assembly 17, including insertion of the support member into aradially-constrictive flexible tubing or sleeve 60, as discussed furtherbelow. The rounded opposed ends may reduce the insertion force used toinsert the support member 50 into the tubing 60 and also the risk of thesupport member 50 tearing and damaging the tubing 60.

In some embodiments, the support member 50, as a round wire, has aninitial (pre-flattening) diameter of about 0.019 inches and a length ofabout 4.25 inches. When flattened, the support member 50 has a generallyrectangular cross-sectional dimensions of about 0.021″×0.015″ from itsproximal end to the location L2. The tapered tail of the support member50 (distal of location L2 in FIG. 6) is about 2.9 inches long and has agenerally rectangular cross-sectional dimensions of about 0.035″×0.008″at or near its distal end 25. In some embodiments, a distal end of thesupport member 50 has an unflattened section 50D which retains its roundcross-section, as explained below in further detail.

The area moment of inertia for the 0.019 inch diameter support member 50(pre-flattening) is the same regardless of centroidal axis orientation,whereas the area moment of inertia at or near its distal end for thefirst centroidal axis is 2.5 times less stiff than the moment of inertiaat the proximal end. The moment of inertia for the second centroidalaxis at the distal end is 4.5 times stiffer than the moment of inertiaat the proximal end. Comparing the two centroidal axis area moments ofinertia at the distal end with respect to each other, the firstcentroidal axis is 18.5 times less stiff than the second centroidalaxis. Since the contraction wire 24 exerts a constant inwardly line offorce (neglecting friction) on the support member 50, to obtain a small,generally circular contraction, the area moment of inertia of thesupport member 50 should constantly decrease towards the distal endwhere it is attached to the contraction wire 24.

The contraction wire 24 has a proximal end anchored in the controlhandle 16 which provides a rotational control knob 59 (see FIG. 1) foractuating the contraction wire 24 via manipulation by an operator. Thecontraction wire 24 extends through the central lumen 18 of the catheterbody 12 (FIG. 3), the sixth lumen 36 of the intermediate section 14(FIG. 4), the central lumen 37 of the connector section 30 (FIG. 5A) andthe fourth lumen 54 of the tubing 56 of the distal assembly 17 (FIG. 8)alongside the support member 50, to the distal end 25 (FIG. 9).

The contraction wire 24 may be covered by a friction-reducing tubing 61(FIG. 8), e.g., a TEFLON® coated inner diameter of a polyimide or PEEKtubing, so that the contraction wire 24 is physically separated andisolated from the side 62 of the support member 50 and the insidesurface of the constrictive tubing 60 that surrounds the contractionwire 24 and the support member 50, which is described below in furtherdetail. The friction-reducing tubing 61 may have a proximal end in theconnector section 30 and a distal end at least distal of the radius R2,at or near the location L2, if not closer to the distal end of thesupport member 50.

Advantageously, the support member 50 and the coextensive segment of thecontraction wire 24 (and its tubing 61) through the lumen 54 of thedistal assembly 17 are surrounded and bound together by thetight-fitting flexible tubing 60.

In some embodiments, as shown in FIG. 6C, the tubing 60 to provideradial constriction includes a woven or braided tubing of a manufacturedfiber, spun from a liquid crystal polymer (LCP), for example,manufactured fiber sold under the trademark

VECTRAN®. Chemically, it is an aromatic polyester produced by thepolycondensation of 4-hydroxybenzoic acid and6-hydroxynaphthalene-2-carboxylic acid. These fibers exhibit thermalstability at high temperatures, high strength and modulus, low creep andgood chemical stability.

The resulting tubing has a high modulus of elasticity which allows forimproved contraction of the distal assembly 17. In some embodiments, themanufactured fiber is braided at high pix per inch (PPI) of about 128and is free of resin so that there is little restriction on the bendingradius of the tubing. A tubing of such manufacture satisfies thestrength required to constrain the contraction wire 24 from tearing thesidewall of the tubing 56. Moreover, the tubing is sufficiently flexibleto allow contraction of the distal assembly 17, and sufficiently strongto withstand frictional fatigue of the contraction wire 24 and othermoving components imposed on the tubing fibers.

In some embodiments, after the tubing 60 has been slipped onto thesupport member 50 and the contraction wire 24, tension force T isapplied to its ends to lengthen longitudinally and shorten radially toprovide a radially constrictive tight fit around the support member 50and the contraction wire 24 in ensuring that the contraction wire 24remains in the proper location relative to the support member 50, thusensuring that the pulling force vector is in alignment with the supportmember 50 for a more efficient loop contraction and improved loopcontraction geometry. The tubing 60 may also be fused to the lumen 54.

In other embodiments, as shown in FIG. 6D, the tubing 60 for radialconstriction has an inner diameter 91 composed of a friction-reducingmaterial, such as, TEFLON®, (formed as a first extrusion coat or layer),which is covered by a stainless steel flat braid 92, which is covered byan outer diameter 93, such as nylon (formed as a second extrusion coator layer). The constrictive tubing 60 is slipped over the support member50 and the contraction wire 24 (with its friction-reducing tubing 61)after their distal ends are affixed together, as described furtherbelow.

In some embodiments, the constrictive tubing 60 has a distal end at ornear a junction of the radii R2 and R3, and a proximal end at or nearthe elbow junction 21. The constrictive tubing 60 is fitted to providecircumferential/radial constriction around the member 50, thecontraction wire 24 with its friction-reducing tubing 61 (see FIG. 8) soas to secure the tubing 61 against the inner side 62 of the supportmember 50 in keeping the contraction wire 24 aligned with (or on theside of) the inner side 62 for improving contraction characteristics ofthe distal assembly 17, including improved circular shape maintenanceand significantly tighter contraction and coiling, as well as improveddurability against the contraction wire 24 cutting into the tubing 56 ofthe distal assembly 17.

Such improved contraction characteristics, particularly of the taperedtail of the distal assembly, is enabled by keeping the contraction 24against the inner side 62 throughout the length of the support member50. For example, where a radius R3 of the arc of distal portion 15 isabout 17mm when the distal assembly 17 is unconstrained, the distalassembly 17 can be contracted into a tighter coil such that the arcs ofthe distal curve portion 21D and the distal portion 15 are both definedby a radius of about 10 mm, for a reduction in the radius R3 of the arcof the distal portion 15 by about 60% or more.

As illustrated in FIG. 6, the contraction wire 24 within its tubing 61runs along the entire length of the inner-facing side 62 of the supportmember 50 extending between the distal end 25 of the distal assembly 17and the connector section 30. This predetermined pattern advantageouslyminimizes any tendency for the contraction wire 24 to separate and liftfrom the support member 50 when the contraction wire 24 is drawnproximally. In some embodiments, the contraction wire 24 may also have arectangular cross-section along its length or along one or more segmentsthereof.

With reference to FIG. 8 and FIG. 9, an assembled structure of thedistal ends of the support member 50, contraction wire 24 andconstrictive tubing 60 is oriented within the fourth lumen 54 of thetubing 56 of the distal assembly 17 such that the contraction wire 24 ismost adjacent to the inner circumference of the distal assembly 17 toface the center of the distal assembly 17. With the fourth lumen 54positioned closer to the inner circumference than the other lumens ofthe tubing 56, and the contraction wire 24 within the lumen 54 alsopositioned closer to the inner circumference than the support member 50,the contraction wire 24 can effectively contract the distal assembly 17.

Prior to insertion into the lumen 54, the assembled structure of thedistal ends of the support member 50, the contraction wire 24 and theconstrictive tubing 60 is prepared. In some embodiments, a coupling ofthe distal ends of the contraction wire 24 and support member 50includes a laser welded coupling having a stainless steel ferrule 65(e.g., 304 or 316 series) that is placed over the distal end 25D of thesupport member 50 which is not flattened but retains its original roundcross-sectional shape. The ferrule 65 is flattened after it is placedover the distal end 25D. The flattened portion of the support member 50acts as a stop preventing any proximal migration or dislocation of theferrule 65 when contraction wire tension is applied to the supportmember 50. The ferrule 65 is secured to the round distal end 50D of thesupport member 50 by a crimp die which has a flat portion that isclocked parallel to the surface 62 of the support member 50. The distalend of the contraction wire 24 has a crimped ferrule 80 which has a flatportion that is also fixed to the flat portion of the ferrule 65. Alaser seam weld 101 is made on one common (bottom) side of the ferrules65 and 80 joining the distal ends of the contraction wire 24 and thesupport member 50.

In contrast to prior art coupling of the support member and thecontraction wire which used lead-free solder to join a nitinol supportmember to the contraction wire, the laser welded coupling describedherein includes the use of strong acid flux to remove oxides from thenitinol and stainless steel before soldering. Moreover, the laser weldedcoupling provides a much stronger attachment compared to the prior artthe lead-free solder with a low shear and tensile strength (about 4000psi) which can attribute to puller wire detachment failures from thenitinol support member when the lead-free solder contained unexposedvoids or was formed as a cold solder joint.

The constrictive tubing 60 is then slid over the contraction wire 24 atits proximal end, advanced over the support member 50 at its proximalend, and further advanced until the distal end of the tubing 60 reachesand covers the assembled structure.

When the constrictive tubing 60 has been properly positioned over thecontraction wire 24 and the support member 50, the constrictive tubing60 has a proximal end near a junction of radii R2 and R3, and it distalend is trimmed or otherwise provided with a finished distal endterminating immediately proximal of the stainless steel ferrule 65. Thefinished distal end of the constrictive tubing 60 is then affixed to thefriction-reducing tubing 61 and the support member 50 by acircumferential application of an adhesive 111, e.g., LOCTITE®. Notably,the friction-reducing tubing 61 surrounding the contraction wire 24 hasa distal end that is well proximal of the soldered stainless steelferrule 65 so that the adhesive 111 can bond the distal end of theconstrictive tubing 60 directly on to the contraction wire 24 and thesupport member 50.

The assembled structure of the contraction wire 24, the support member50 and the constrictive tubing 60 is then inserted into the lumen 54,where the stainless steel ferrule 65 and its contained components arefixed and anchored at the distal end of the multi-lumened tubing 56 byan adhesive 64, e.g., polyurethane, which covers the entire distal faceof the distal end 25 to form a tip dome, as shown in FIG. 9. With thisarrangement, the relative positions of the contraction wire 24 and thesupport member 50 can be controlled so that the contraction wire 24 ispositioned on or near the inner circumference of the distal assembly 17,closer to the center of the spiral-helical form, as described above. Theconstrictive tubing 60 protects the multi-lumened tubing 56 from thecontraction wire 24 cutting into its side wall during contraction of thedistal assembly 17.

With reference to FIG. 3 and FIG. 4, a compression coil 68 surroundingthe contraction wire 24 extends from the proximal end of the catheterbody 12 and through the entire length of the sixth lumen 36 of theintermediate section 14. Thus, the compression coil has a distal end ator near a mid-location in the connector section 30. The compression coil68 is made of any suitable metal, preferably stainless steel, and istightly wound on itself to provide flexibility, i.e., bending, but toresist compression. The inner diameter of the compression coil ispreferably slightly larger than the diameter of the contraction wire 24.The outer surface of the compression coil is covered by a flexible,non-conductive sheath 67, e.g., made of polyimide tubing. Thecompression coil preferably is formed of a wire having a square orrectangular cross-sectional area, which makes it less compressible thana compression coil formed from a wire having a circular cross-sectionalarea. As a result, the compression coil 68 keeps the catheter body 12,and particularly the intermediate section 14, from deflecting when thecontraction wire 24 is drawn proximally to contract the distal assembly17, as the compression coil 68 absorbs more of the compression.

The ring electrodes 19 are mounted on predetermined locations on thedistal portion 15, as shown in FIG. 2A and FIG. 2B. The electrodes canbe made of any suitable solid conductive material, such as platinum orgold, preferably a combination of platinum and iridium or gold andplatinum, and mounted onto the tubing with glue or the like. A suitableembodiment of an electrode adapted for ablation and irrigation isillustrated in FIG. 10. An ablation reservoir (“AR”) electrode isgenerally cylindrical with a length greater than its diameter. In oneembodiment, the length is about 3.0 mm, the outer diameter is about 2.8mm, and the inner diameter is about 2.33 mm.

In some embodiments, the plurality of AR ring electrodes 19 on thedistal assembly 17 can ranges from about six to about twenty, morepreferably from about eight to about twelve. In some embodiments, thedistal assembly 17 carries ten AR electrodes. The electrodes can beapproximately evenly spaced along the distal portion 15.

The proximal end of each wire of the wire pairs 40, 41 is electricallyconnected to a suitable connector (not shown) distal of the controlhandle 16. In the disclosed embodiment, wire 40 of a wire pair is acopper wire, e.g. a number “40” copper wire, and the other wire 41 ofthe wire pair is a constantan wire. The wire pairs extend from thecontrol handle 16, through the central lumen 18 of the catheter body 12(FIG. 3), the first lumen 31 of the intermediate section 14 (FIG. 4),the central lumen 37 of the connector section 30 (FIG. 5A), and thesecond lumen 52 of the distal assembly 17 (FIG. 8). The distal ends ofthe wire pairs pass through holes 74 (FIG. 9) formed in the side wall ofthe tubing 56 to reach the AR electrodes 19. The wires of each pair areelectrically isolated from each other except at their distal ends wherethey are exposed. Exposed distal ends of a respective wire pair 40, 41are sandblasted, and wrapped in and welded to a folded metal foil 72(e.g., copper foil) which is then welded to an inner surface 70 near aproximal end 71 of its AR electrode 19, as shown in FIG. 10.

Ablation energy, e.g., RF energy, is delivered to the AR electrodes 19via the wire 40 of the wire pairs. However, the wire pairs inclusive oftheir respective constantan wire 41 can also function as temperaturesensors or thermocouples sensing temperature of each AR electrode 19.

All of the wire pairs pass through one nonconductive protective sheath39 (FIG. 3 and FIG. 4), which can be made of any suitable material,e.g., polyimide, in surrounding relationship therewith. The sheath 39extends with the wire pairs from the control handle 16, the catheterbody 12, the intermediate section 14, the connector section 30 and intothe second lumen 52 of the distal assembly 17, terminating just distalof the junction between the connector section 30 and the distal assembly17, for example, about 5 mm into the second lumen 52. The distal end isanchored in the second lumen 52 by glue, for example, polyurethane glueor the like.

Irrigation fluid is delivered to the distal assembly by the irrigationtubing 43 whose proximal end is attached to a luer hub 73 (FIG. 1)proximal of the control handle 16 and receives fluid delivered by a pump(not shown). The irrigation tubing 43 extends through the control handle16, the central lumen 18 of the catheter body 12 (FIG. 3), the secondlumen 32 of the intermediate section 14 (FIG. 4), the central lumen 37of the connector section 30 (FIG. 5A) and a short distance, e.g., about5 mm, distally into the third lumen 53 of the multi-lumened tubing 56 ofthe distal assembly 17. The fluid enters the third lumen 53 where itexits via openings (not shown) formed in the sidewall of the tubing 56to enter the AR ring electrodes 19 and exits apertures 78 formed in theelectrode side wall (FIG. 10). It is understood that the distal portion15 may carry any form of electrodes, including the aforementioned ARring electrodes, impedance ring electrodes, and/or combinations thereof,as desired or appropriate.

The deflection puller wire 44 is provided for deflection of theintermediate shaft 14. The deflection wire 44 extends through thecentral lumen 18 of the catheter body 12 (FIG. 3) and the third lumen 33of the intermediate section 14 (FIG. 4). It is anchored at its proximalend in the control handle 16, and at its distal end to a location at ornear the distal end of the intermediate section 14 by a T-bar 76 (FIG.4) that is affixed to the sidewall of the tubing 15 by suitablematerial, e.g., polyurethane 69 . The puller wire 54 is made of anysuitable metal, such as stainless steel or Nitinol, and is preferablycoated with TEFLON® or the like. The coating imparts lubricity to thepuller wire. The puller wire 44 may have a diameter ranging from about0.006 to about 0.010 inch.

A second compression coil 47 is situated within the central lumen 18 ofthe catheter body 12 in surrounding relation to the puller wire 44 (FIG.3). The second compression coil 47 extends from the proximal end of thecatheter body 12 to at or near the proximal end of the intermediatesection 14. The second compression coil 47 is made of any suitablemetal, preferably stainless steel, and is tightly wound on itself toprovide flexibility, i.e., bending, but to resist compression. The innerdiameter of the second compression coil 47 is preferably slightly largerthan the diameter of the puller wire 44. A TEFLON® coating (not shown)on the puller wire allows it to slide freely within the secondcompression coil. Within the catheter body 12, the outer surface of thesecond compression coil 47 is covered by a flexible, non-conductivesheath 49, e.g., made of polyimide tubing. The second compression coil47 is anchored at its proximal end to the outer wall 20 of the catheterbody 12 by a proximal glue joint and to the intermediate section 14 by adistal glue joint.

Within the third lumen 33 of the intermediate section 14, the pullerwire 44 extends through a plastic sheath (not shown) , preferably ofTEFLON®, which prevents the puller wire 44 from cutting into the wall ofthe tubing 23 of the intermediate section 14 when the intermediatesection 14 is deflected.

Longitudinal movement of the contraction wire 24 relative to thecatheter body 12, which results in contraction of the spiral-helicalform of the distal assembly 17, is accomplished by suitable manipulationof the control handle 16. Similarly, longitudinal movement of thedeflection wire 44 relative to the catheter body 12, which results indeflection of the intermediate section 14, is accomplished by suitablemanipulation of the control handle 16. Suitable control handles formanipulating more than one wire are described, for example, in U.S. Pat.Nos. 6,468,260, 6,500,167, and 6,522,933, the entire disclosures ofwhich are incorporated herein by reference.

In one embodiment, the catheter includes a control handle 16 as shown inFIG. 11 and FIG. 12. The control handle 16 includes a deflection controlassembly that has a handle body 84 in which a core 86 is fixedly mountedand a piston 87 is slidably mounted over a distal region of the core 86.The piston 87 has a distal portion that extends outside the handle body.A thumb knob 58 is mounted on the distal portion so that the user canmore easily move the piston 87 longitudinally relative to the core 86and handle body 84.

The proximal end of the catheter body 12 is fixedly mounted to thedistal end of the piston 87. An axial passage 88 is provided at thedistal end of the piston 87, so that various components, including leadwires 40, 41, contraction wire 24, deflection wire 44, position sensingcable assembly 48 and irrigation tubing 43 that extend through thecatheter body 12 can pass into the control handle. The lead wires 40, 41can extend out the proximal end of the control handle 16 or can beconnected to a connector that is incorporated into the control handle,as is generally known in the art. The irrigation tubing 43 can alsoextend out the proximal end of the control 16 for connection with anirrigation source (not shown) via a luer hub.

The proximal end of the deflection wire 44 enters the control handle 16,and is wrapped around a pulley 83 and anchored to the core 86.Longitudinal movement of the thumb knob 58 and piston 87 distallyrelative to the handle body 84 and core 86 draws the proximal end of thedeflection wire 44 distally. As a result, the deflection wire 44 pullson the side of the intermediate section 14 to which it is anchored,thereby deflecting the intermediate section in that direction. Torelease and straighten the intermediate section 14, the thumb knob 58 ismoved proximally which results in the piston 87 being moved proximallyback to its original position relative to the handle body 84 and core86.

The control handle 16 is also used for longitudinal movement of thecontraction wire 24 via a rotational control assembly. In theillustrated embodiment, the rotational control assembly includes a camhandle 81 and a cam receiver 82. By rotating the cam handle in onedirection, the cam receiver is drawn proximally to draw on thecontraction wire 24. By rotating the cam handle in the other direction,the cam receiver is advanced distally to release the contraction wire24. The contraction wire 24 extends from the catheter body 12 into thecontrol handle 16, through the axial passage in the piston 88 andthrough the core 86 to be anchored in an adjuster 85 by which tension onthe contraction wire can be adjusted.

In one embodiment, the position sensor cable assembly 48 including aplurality of single axis sensors (“SAS”) extends through the first lumen51 of the distal assembly 17 (FIG. 8), where each SAS occupies a knownor predetermined position on the spiral-helical form of the distalassembly 17. The cable assembly 48 extends proximally from the distalassembly 17 through the central lumen 37 of the connector section 30,the fourth lumen 34 of the intermediate section 14 (FIG. 4), the centrallumen 18 of the catheter body 12 (FIG. 3), and into the control handle16. Each SAS can be positioned with a known and equal spacing separatingadjacent SASs. In the disclosed embodiment, the cable carries three SASsthat are positioned under the distal-most AR electrode, theproximal-most AR electrode, and a mid AR electrode, for sensing locationand/or position of the distal assembly 17. The SASs enable thespiral-helical form to be viewed under mapping systems manufactured andsold by Biosense Webster, Inc., including the CARTO, CARTO XP and NOGAmapping systems. Suitable SASs are described in U.S. Pat. No. 8,792,962,the entire disclosure of which is incorporated herein by reference.

The preceding description has been presented with reference to presentlypreferred embodiments of the invention. Workers skilled in the art andtechnology to which this invention pertains will appreciate thatalterations and changes in the described structure may be practicedwithout meaningfully departing from the principal, spirit and scope ofthis invention. Any feature or structure disclosed in one embodiment maybe incorporated in lieu of or in addition to other features of any otherembodiments, as needed or appropriate. As understood by one of ordinaryskill in the art, the drawings are not necessarily to scale.Accordingly, the foregoing description should not be read as pertainingonly to the precise structures described and illustrated in theaccompanying drawings, but rather should be read consistent with and assupport to the following claims which are to have their fullest and fairscope.

What is claimed is:
 1. An electrophysiology catheter comprising: anelongated catheter body; a contraction wire; a distal assemblyconfigured for contraction by actuation of the contraction wire, thedistal assembly having a shape-memory support member having a 3-Dconfiguration, the distal assembly including a radially-constrictivetubing surrounding the shape-memory support member and a coextensiveportion of the contraction wire.
 2. The catheter of claim 1, wherein theradially-constrictive tubing is transparent.
 3. The catheter of claim 1,wherein the radially-constrictive tubing is translucent.
 4. The catheterof claim 1, wherein the radially-constrictive tubing has a wovenconstruction.
 5. The catheter of claim 1, wherein theradially-constrictive tubing has a braided construction.
 6. The catheterof claim 1, wherein the radially-constrictive tubing includesmanufactured fibers formed from a liquid crystal polymer.
 7. Thecatheter of claim 1, wherein the support member has an inner side facingan inner circumference of the 3-D configuration, and wherein thecoextensive portion of the contraction wire extending through the distalassembly is aligned with the inner side.
 8. The catheter of claim 1,wherein the distal assembly carries a plurality of ring electrodes. 9.An electrophysiology catheter comprising: an elongated catheter body; acontraction wire; and a 3-D arcuate distal assembly configured forcontraction by the contraction wire, the distal assembly defining aninner circumference, the distal assembly having: a first tubing with alumen on or near the inner circumference an elongated support memberextending through the lumen, the support member having a longitudinalflat side, the contraction wire extending through the lumen and having acoextensive segment alongside the flat side of the support member; and aradially-constrictive braided tubing extending through the lumen andcircumferentially surrounding the support member and the coextensivesegment of the contraction wire.
 10. The catheter of claim 9, whereinthe support member and the coextensive segment of the contraction wirejointly define a cross-sectional profile, and the radially-constrictivebraided tubing surrounds the support member and the coextensive segmentgenerally in conformity to the cross-sectional profile.
 11. The catheterof claim 9, wherein the coextensive portion of the contraction wire isaligned with a flat side of the support member, and wherein theradially-constrictive braided tubing is configured to maintain thecoextensive segment of the contraction wire generally in alignment witha flat side of the support member during contraction of the distalassembly.
 12. The catheter of claim 9, wherein the radially-constrictivebraided tubing is configured to maintain the coextensive segment of thecontraction wire alongside the flat side of the support member.
 13. Thecatheter of claim 9, wherein the radially-constrictive tubing istransparent.
 14. The catheter of claim 9, wherein theradially-constrictive tubing is translucent.
 15. The catheter of claim9, wherein the radially-constrictive tubing has a woven construction.16. The catheter of claim 9, wherein the radially-constrictive tubinghas a braided construction.
 17. The catheter of claim 9, wherein theradially-constrictive tubing includes manufactured fibers formed from aliquid crystal polymer.
 18. An electrophysiology catheter having: anelongated catheter body defining a longitudinal axis; a contractionwire; and a 3-D distal assembly movable between a neutral configurationand a contracted configuration in response to longitudinal movement ofthe contraction wire, the 3-D distal assembly including a shape-memorysupport member and a radially-constrictive tubing of braidedconstruction, wherein the 3-D distal assembly has an elbow junction anda distal portion, the elbow junction defined by at least a proximaldiameter and the distal portion defined by a distal diameter, whereinfor the neutral configuration, the proximal diameter is less than thedistal diameter and wherein for the contracted configuration, the distaldiameter is about equal to or less than the proximal diameter, and 19.The electrophysiology catheter of claim 18, wherein theradially-constrictive tubing includes fibers of spun liquid crystalpolymer.
 20. The electrophysiology catheter of claim 18, wherein theradially-constrictive tubing has a distal end generally proximal of thedistal portion, and a proximal end at or near the elbow junction.